Disk Utility Icon

Erasing disks securely

Usually when you erase a disk or volume, Disk Utility only erases the information used to access the files on the disk, not the actual files. Because of this, the erased files can be recovered.

If you want to erase the files so that they cannot be recovered, you can select security options to write zeros over the disk space. To make it more difficult to recover the files on the disk, you can specify doing this once, seven times, or 35 times. If you have a large disk, overwriting the free space several times can take a long time.

  1. In Disk Utility, select the disk you want to erase and click Erase.
  2. Specify a volume format and name for the disk.
  3. Click Security Options and select the option you want to use. Click OK.
  4. Click Erase.

If you select your startup disk, the buttons are dimmed because you can't erase your startup disk. To erase your computer's startup disk, you must start up from another disk. You can use your Mac OS X Install disc or the Software Restore disc that came with your computer.

See also

erasing disks